Front lowering spring issues - The 1947 - Present Chevrolet & GMC Truck Message Board Network

grschell · 08-20-2019, 12:14 PM

Hello all. I am having a few issues with lowering the front of my 70 GMC C-15. I decided to replace the control arm shafts, ball joints, and tie rod ends while it was apart. First thing I found out was the spindles (and maybe the control arms) were from a later model truck. The '70 model ball joints were shorter than the ones I took out and the new lower ball joint was a smaller diameter where it presses into the lower control arm . I ended up having to use '72 ball joints. When I put the 3" lowered springs in and connected the upper and lower ball joints through the spindle, the springs were completely loose when the upper control arm was topped out (resting on the spring perch). I know that the springs can't be that loose because I can pop them off of the tapered cup in the top of the perch. I would think that if the suspension ever topped out, the springs would not stay in position and that would be a BAD thing. Is this a known issue with lowered springs? The new 3" drop springs are about 1-1/2" shorter than the ones I took out. Anyone else run into this? I wonder if the later model spindles are taller, thus causing the loose springs. Any ideas?

grschell · 08-20-2019, 12:25 PM

Also, I just realized that I do not have a bump stop in the upper control arm (previous owner must have removed it). Would that alleviate the loose spring issue?

demian5 · 08-20-2019, 12:29 PM

Sounds like you have 72 cross member? Other may know better. Do the brake hoses attach to the front or the back of the cross member? If the hoses go into the frame itself, that tells me you have a 73 and up one in there. I am sure there are others that know better.
The bump stops may help with that, but that is a drop spring issue in general. Welcome to the "hey I just got my oil changed/tires rotated now my vehicle pops/leans to one side" family...

PepperTreeGarage · 08-20-2019, 05:04 PM

Went through this with our C20. Front drop springs need shorter shocks, so that at full droop the springs have just enough tension on them so they don't get loose in the pocket. Here's a partial chart from CPP. There are others available on the net depending on your shock of choice. You may want to consider adding an upper shock mount stiffener also.

grschell · 08-20-2019, 05:52 PM

Thank you for the responses. I do know that I need to add an upper control arm bump stop. I did have the shock off when I was reinstalling the spring. Is it not an issue that the suspension travel is limited by the shock being at maximum length? Seems like a lot of force for the shock to absorb (funny!).

PepperTreeGarage · 08-21-2019, 01:27 AM

With your 3" drop springs. The stock length shock will most likely bottom out before the lower bump stops kick in. The upper bump stops will still allow the short spring to get loose at full droop. The shock chart shows the Extended and Compressed lengths for lowered 1-2", 3", and stock height. It does make a difference. Don't forget to shorten your lower bump stops by 2"-3" inches, otherwise you'll be riding on them. Good Luck.

grschell · 08-21-2019, 05:41 PM

Awesome information people! I have yet to buy shocks, so this will come in handy. Before I attempt the springs again, I have to replace the broken driver's side lower control arm (shaft threads are trashed). I am pretty sure that the spindle is a 72, so I picked up a 72 lower control arm from our local salvage yard. I will tackle that this weekend!

08-20-2019, 12:14 PM	#1
grschell Registered User Join Date: Apr 2019 Location: Norman, OK Posts: 10	Front lowering spring issues Hello all. I am having a few issues with lowering the front of my 70 GMC C-15. I decided to replace the control arm shafts, ball joints, and tie rod ends while it was apart. First thing I found out was the spindles (and maybe the control arms) were from a later model truck. The '70 model ball joints were shorter than the ones I took out and the new lower ball joint was a smaller diameter where it presses into the lower control arm . I ended up having to use '72 ball joints. When I put the 3" lowered springs in and connected the upper and lower ball joints through the spindle, the springs were completely loose when the upper control arm was topped out (resting on the spring perch). I know that the springs can't be that loose because I can pop them off of the tapered cup in the top of the perch. I would think that if the suspension ever topped out, the springs would not stay in position and that would be a BAD thing. Is this a known issue with lowered springs? The new 3" drop springs are about 1-1/2" shorter than the ones I took out. Anyone else run into this? I wonder if the later model spindles are taller, thus causing the loose springs. Any ideas?

08-20-2019, 12:25 PM	#2
grschell Registered User Join Date: Apr 2019 Location: Norman, OK Posts: 10	Re: Front lowering spring issues Also, I just realized that I do not have a bump stop in the upper control arm (previous owner must have removed it). Would that alleviate the loose spring issue?

08-20-2019, 12:29 PM	#3
demian5 Registered User Join Date: Aug 2016 Location: Lake Forest, CA Posts: 2,178	Re: Front lowering spring issues Sounds like you have 72 cross member? Other may know better. Do the brake hoses attach to the front or the back of the cross member? If the hoses go into the frame itself, that tells me you have a 73 and up one in there. I am sure there are others that know better. The bump stops may help with that, but that is a drop spring issue in general. Welcome to the "hey I just got my oil changed/tires rotated now my vehicle pops/leans to one side" family... __________________ "Work hard, use your vacation days." 1970 C15 GMC Long Bed 1986 C20 Scottsdale 1983 K2500 Sierra Classic Suburban 6.2 Instagram: C10sofOC

08-20-2019, 05:04 PM	#4
PepperTreeGarage Registered User Join Date: Jan 2014 Location: SoCal Posts: 281	Re: Front lowering spring issues Went through this with our C20. Front drop springs need shorter shocks, so that at full droop the springs have just enough tension on them so they don't get loose in the pocket. Here's a partial chart from CPP. There are others available on the net depending on your shock of choice. You may want to consider adding an upper shock mount stiffener also. Attached Images

08-20-2019, 05:52 PM	#5
grschell Registered User Join Date: Apr 2019 Location: Norman, OK Posts: 10	Re: Front lowering spring issues Thank you for the responses. I do know that I need to add an upper control arm bump stop. I did have the shock off when I was reinstalling the spring. Is it not an issue that the suspension travel is limited by the shock being at maximum length? Seems like a lot of force for the shock to absorb (funny!).

08-21-2019, 01:27 AM	#6
PepperTreeGarage Registered User Join Date: Jan 2014 Location: SoCal Posts: 281	Re: Front lowering spring issues With your 3" drop springs. The stock length shock will most likely bottom out before the lower bump stops kick in. The upper bump stops will still allow the short spring to get loose at full droop. The shock chart shows the Extended and Compressed lengths for lowered 1-2", 3", and stock height. It does make a difference. Don't forget to shorten your lower bump stops by 2"-3" inches, otherwise you'll be riding on them. Good Luck. Attached Images

08-21-2019, 05:41 PM	#7
grschell Registered User Join Date: Apr 2019 Location: Norman, OK Posts: 10	Re: Front lowering spring issues Awesome information people! I have yet to buy shocks, so this will come in handy. Before I attempt the springs again, I have to replace the broken driver's side lower control arm (shaft threads are trashed). I am pretty sure that the spindle is a 72, so I picked up a 72 lower control arm from our local salvage yard. I will tackle that this weekend!



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